Mortality from toxic shock, caused by infective agents that trigger excessive synthesis of tumor necrosis factor (TNF) and other inflammatory molecules by macrophages, remains a major health problem. Here we describe for the first time resistance to lipopolysaccharide (LPS) and TNF-induced death in vivo of wild-derived mice of MSM strain, representing a new genetic model of resistance to toxic shock. The remarkable resistance of these mice to toxic shock is further emphasized by their lack of sensitivity to acute liver injury caused by the co-administration of TNF and D-galactosamine, a well-established in vivo model of endotoxic liver damage. In support of the in vivo resistance data, we show that primary MSM macrophages exhibit another phenotype in that they are resistant to TNF- or TLR-agonists-induced regulated necrosis ("necroptosis") but not apoptosis cell death in vitro. Based on these results, we hypothesize that the two traits are mechanistically linked and propose to examine the connection between necroptosis and toxic shock traits by means of genetic linkage analysis aimed at identification of the loci, which confer both traits. In further extension of the in vitro results, we discovered that TNF-mediated in vivo liver injury can be prevented by a specific inhibitor of a key necroptosis regulator, RIP1 kinase. In addition to cell death phenotype, we demonstrate that TNF synthesis by MSM macrophages is reduced and may also be influenced by RIP1 signaling in vivo. Based on our preliminary data, we suggest that RIP1 kinase is a mediator of acute toxic shock and may represent an important new target for therapeutic intervention. We propose to further characterize the scope of changes in in vitro MSM hepatocyte and macrophage responses to TLR agonists and TNF in order to better determine the cellular basis for MSM resistance to toxic shock. Overall, these studies may provide important new insights into mechanisms of both toxic shock in vivo and necroptotic RIP1 kinase signaling, which has also been implicated in other acute pathologies, such as stroke, myocardial infarction and brain trauma. PUBLIC HEALTH RELEVANCE: Mortality from toxic shock, caused by infective agents that trigger excessive synthesis of tumor necrosis factor (TNF) and other inflammatory molecules by macrophages remains a major health problem. In this proposal, using genetic analysis of resistance to toxic shock in the wild-derived mice, we will reveal novel mechanisms of control of inflammation and its magnitude.